Hardware Setup

GopherTrunk ships with a pure-Go RTL-SDR driver — no librtlsdr, libusb, or C toolchain on the build host. The daemon talks to RTL2832U dongles directly through the platform’s USB stack (USBDEVFS ioctls on Linux, WinUSB on Windows; macOS lands in a follow-up — see issue #82).

Supported devices

The same code path covers everything librtlsdr did — RTL2832U paired with R820T / R820T2 / R828D / E4000 / FC0012 / FC0013 / FC2580. Tuner detection is automatic on Open.

Tested combinations:

Device	Tuner	Notes
NooElec NESDR Smart v5	R820T2	0.5 ppm TCXO, software-controllable bias-tee. Use bias_tee: true in config to power an external LNA via the SMA.
NooElec NESDR Smart (v4 and earlier)	R820T2	TCXO; no bias-tee on early units.
Generic RTL-SDR Blog v3 / v4	R820T2 / R828D	Bias-tee on most units.
Plain RTL2832U DVB-T sticks	R820T	No TCXO; expect a few ppm offset — set ppm: in config after measuring.

If you have a v5 (or any modern dongle with a bias-tee) and want to power an LNA, the config snippet looks like:

sdr:
  devices:
    - serial: "00000001"      # whatever `gophertrunk sdr list` shows
      role: control            # or voice / auto
      ppm: 0                   # 0 is fine for TCXO-equipped units
      gain: "auto"             # or a numeric tenths-of-dB string like "496"
      bias_tee: true           # 5V on the SMA — only enable if you want it

Linux

No package install is needed for the build itself; the driver only needs USB-device permissions at runtime.

Add a udev rule so non-root processes can claim the dongle:

# /etc/udev/rules.d/20-rtlsdr.rules
SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2838", MODE="0666"

Reload udev (sudo udevadm control --reload && sudo udevadm trigger) and unplug/replug the dongle.

Blacklist the kernel’s DVB driver, which otherwise grabs the device first:

# /etc/modprobe.d/blacklist-dvb_usb_rtl28xxu.conf
blacklist dvb_usb_rtl28xxu

Windows

Bind the dongle to WinUSB with Zadig once per device — see docs/install-windows.md for the click-by-click walkthrough.

Verifying the build

make build
./bin/gophertrunk sdr list

You should see one row per attached dongle with index, serial, tuner type (usually R820T2 or R828D), and the supported gain values. The Driver column reads rtlsdr for every entry.

Capturing IQ for replay

The mock driver replays raw u8-IQ files (.cfile format). You can generate one with any tool that produces interleaved unsigned-8-bit samples — e.g. gqrx’s baseband recorder or a dedicated capture utility. Drop .cfile files under testdata/iq/ to use them through the mock driver.